This invention relates generally to missiles and more particularly to apparatus for attaching wings to missiles.
Missiles in flight are controlled and stabilized by wings attached to the missile body. The wings, however, can be easily damaged while the missile is being transported or stored before it is fired. To avoid damage and to facilitate mounting the missile on an airplane, the wings are often made so that they can be detached while the missile is being transported and then quickly installed after the missile is loaded on an airplane.
One removable wing design uses a "locking ball". The wing includes a post. A plurality of balls are fabricated in the end of the post. The balls can retract into the post or be locked in a position protruding from the post. The missile is made with a hole (also called a "bore") large enough to receive the post and balls when retracted.
To attach the wing, the post is inserted into the bore until the portion of the post with the balls extends through the bore. A locking mechanism then releases the balls and they prevent the post from sliding back out of the bore. Since the balls cannot fit through the bore, the wing is attached to the missile.
To prevent the wing from rotating around the post, a pin is attached to the surface of the wing which butts against the missile. The pin fits into a hole in the missile body.
This method of attaching wings is adequate for many applications. However, this method of attachment may not be adequate to prevent the wing from fluttering or vibrating in the presence of air turbulence as the missile flies. The problem of wing vibration is exacerbated because the pin and the hole into which the pin fits tend to wear away as the wing vibrates. As the pin fits less snugly into the hole, the vibration becomes worse.
A small amount of vibration and wear caused by vibration of the wing is acceptable. Too much wear, however, degrades the performance of the missile. Over time, the wing vibration will increase until the wear becomes unacceptably large, allowing the wing to flutter. In designing a missile, the means for securing the wing must keep the wing vibration and wear at acceptable levels over the useful life of the missile. For missiles which are carried on airplanes before they are fired, wing vibration while the missile is mounted on the airplane must also be considered.
Air turbulence is a very complicated phenomenon. While models of airplanes and missiles in flight can be used to estimate air turbulence, the actual amount of turbulence in some situations may deviate sharply from the amount predicted by the models. A missile designer, therefore, may underestimate the amount of turbulence a missile wing is exposed to over its life. Consequently, the method of attaching wings to missiles may not be adequate to keep wing flutter at acceptable levels over the lifetime of the missile.
When it is discovered that the design of a missile is inadequate for any reason, it is often very difficult and costly to change the design. Every design change must be carefully evaluated to determine its impact on the performance of the missile. For example, the impact on performance of any added weight or drag of any change must be determined.
Changing the method of attaching wings poses unique problems. It is often necessary for aerodynamic reasons to mount a set of wings over the motor of the missile. If changing the method of attaching wings requires recessing parts into the missile or attaching parts to the missile, changes to the motor may be needed. Since the motor comprises a highly pressurized vessel, any changes to the motor must be carefully scrutinized. It must be determined that the changes to the motor design do not create weaknesses in the pressurized vessel. The testing needed to make this determination is very time consuming and undesirable.